For many years, liquids, such as soaps, sanitizers, cleansers, disinfectants, and the like have been dispensed through the use of user-actuated pumps. The pump mechanism employed with such dispensers has typically been a liquid pump, simply emitting a predetermined quantity of the liquid upon movement of an actuator. Recently, for purposes of effectiveness and economy, it has become desirable to dispense the liquids in the form of foam, generated by the interjection of air into the liquid. Accordingly, the standard liquid pump has given way to a foam generating pump, which necessarily requires means for combining the air and liquid in such a manner as to generate the desired foam.
Typically, foam pumps include an air pump portion and a fluid pump portion—the two requiring communication to ultimately create the foam. One type of foam pump, such as those shown in U.S. Pat. Nos. 5,271,530 and 5,445,288, employs air and liquid pistons that move within respective air and liquid piston housings and employ valves to drawn air and liquid from separate sources and direct them into a common chamber and/or through a screen member to create a foam product. This invention improves upon such piston-based dispensers.